Extract tissue/lineage & prepare input for scVelo, which is Python-based

Working directory should contain root atlas Seurat object, which is available on GEO under record GSE152766:

Root_Atlas.rds (or get it by running through notebook 2, 3, 4, 5, 6 & 7)
Root_Atlas_spliced_unspliced_raw_counts.rds

1. Extract Ground Tissue

2. Extract Epidermis + LRC

3. Extract Columella

4. Extract Stele